Im,19,ill be 20. had a positive opk on the 26 an 27 of July,my period was due the 11. I have taken pregnancy tests at 25 MIU an they are negative. I use opks to predict when I ovulate so I won't get pregnant if that makes sense. I've been protected everytime I've had sex. With condoms. Also,I've been very stressed out over ALOT of things lately. Can that have caused me to skip my period completely.